This feature allows administrators to define custom CSS classes for individual HTML blocks.
It enhances styling flexibility and integrates with common grid systems (e.g., Bootstrap `col-md-6`)
by applying user-defined classes to the block's wrapper element.
Includes:
- A new `custom_class` field in the block model, form, and data handlers.
- Database schema updates with an upgrade path to handle potential renames from `column_class`.
- Frontend rendering to apply the classes.
- Registration of `actionFrontControllerSetMedia` hook to load front-end CSS.
- Basic responsive image styling for blocks.
isabelle